Connection of semiconductor devices, such as integrated circuits, has become increasingly difficult as the number of pins on the device increases. An example of such a device is a pin grid array package having a plurality of pins which plug into holes in a printed circuit board so that a reliable soldered connection can be made. Such solder connections provide good electrical contact and have good mechanical properties. However, a soldered connection is in essence a permanent connection and it is often difficult to remove such a package without damaging it or the board.
In order to provide a removable connection, it is common to pre-attach a spring-loaded retaining socket to the circuit board and to rely on the spring characteristics of the socket to retain the components in place. As the number of pins in a package increases, the amount of force required to overcome the cumulative resistance of a corresponding number of sockets may be so great that either the package and/or the circuit board becomes damaged by insertion or removal of the package.
U.S. Pat. No. 3,763,459 to Millis discloses a plug-in type socket for making temporary electrical connections with such packages without applying substantial insertion pressure. Millis discloses the mechanical actuation of a plurality of contact elements by a single actuating means. U.S. Pat. No. 3,315,212 to Peterson discloses a multi-pin connector assembly, including a cam-actuated movable connector block mounting flexible contacts. The mechanical retaining force of the above-mentioned devices is not always satisfactory particularly where the devices are exposed to shock or vibration. As a result, the Millis and Peterson type devices are limited to the temporary testing and evaluating of packages.
An extremely reliable contact which can be pre-soldered into a printed circuit board and which exerts a very strong retaining force on electrical components such as pins, after they are installed, is disclosed in commonly assigned U.S. Pat. No. 3,740,839. This patent discloses a resilient member such as a forked member fabricated from beryllium copper, having at least two tines capable of being moved inwardly, and when so moved, to exert an outward force on the means which is moving them inwardly. A band of heat-recoverable metallic material, for example, of a suitable alloy of titanium nickel, is placed around the exterior of the tines. When the metallic band is at a first temperature, it will be in its austenitic state, during which state it will have substantial strength and will attempt to assume a small diameter condition with the result that the tines will be pressed inwardly against any object inserted between them. Commonly assigned U.S. Pat. No. 3,861,030 utilizes a plurality of these individual contacts mounted with a plurality of tabs depending from an elongated carrier strip. It can be appreciated that as the number of contacts increase, the complexity and the cost of such a connector increases dramatically.